Firmware of a storage device may be updated in order to cope with failure of the storage device or to add a new function to the storage device. An example of related art includes a technique in which, when a command to update firmware of a disk device is received, a disk device of which firmware is to be updated is designated on the basis of contents of the command to update firmware and the designated disk device is disconnected to be temporarily degenerated. Another example includes a technique in which first and second disk control units operable in parallel are included, and firmware of the first disk control unit is updated while the second disk control unit executes a command in place of the first disk control unit.
Related techniques are disclosed in, for example, Japanese Laid-open Patent Publication No. 2009-075716 and Japanese Laid-open Patent Publication No. 2010-117970.
However, according to the related arts, performance of access to data of a first type storage device may be degraded while firmware of a plurality of a second type storage devices serving as caches of the first type storage device is being updated. Specifically, for example, a request to access data of the first type storage device, which is temporarily stored in a certain storage device among the plurality of second type storage devices, may be generated while firmware of the certain storage device is being updated. In this case, since the certain storage device is unavailable, the data of the first type storage device is not cached and access performance is degraded.